TRYPANOSOMA OF SLEEPING SICKNESS 559 



realised the significance of the observation, urged Castellani to 

 further inquiries, which he himself continued after the departure 

 of the latter, with the result that in a series of examinations 

 carried out in several infected localities, the trypanosome was 

 demonstrated in every case of the disease. This work formed 

 the starting-point for inquiries, the results of which make it 

 practically certain that the parasite is the causal agent of the 

 condition. The organisms were not demonstrable in the cerebro- 

 spinal fluid of patients dying of other diseases in the sleeping sick- 

 ness area. On the other hand, it was found that if cerebro-spinal 

 fluid withdrawn from cases of the disease was injected into monkeys 

 (especially macacus rhesus) trypanosomes appeared in the blood, 

 and in many cases in three or four months the animals died of an 

 illness indistinguishable from sleeping sickness and with the para- 

 sites in the central nervous system. It was further found that in 

 the parts round the north end of Victoria Nyanza where sleeping 

 sickness was rife, the distribution of the disease exactly corre- 

 sponded with the distribution of a blood-sucking insect, the 

 glossina palpalis, a species closely allied to the glossina morsitans 

 of nagana. It was found that, when one of these flies was fed on 

 a sleeping sickness patient and then allowed to bite a monkey, 

 frequently trypanosomes appeared in the animal's blood, and 

 that when fresh flies caught in the sleeping sickness area were 

 placed on a monkey a similar occurrence took place. 



The trypanosome of sleeping sickness is 17-28 /A long and 

 1*4-2 //. broad (Fig. 169) (when about to divide it is both longer 

 and broader). According to Laveran the free part of the 

 flagellum often equals a fourth of the whole length, but occasion- 

 ally the body protoplasm extends quite to the end of the 

 organism. The undulating membrane is narrow, and the 

 posterior end may be either sharp or blunt. The trypanosome 

 contains the macro- and micronucleus characteristic of the group, 

 and the protoplasm often shows chromatin granules. Castellani 

 attached great importance to a vacuole often seen in the neigh- 

 bourhood of the micronucleus, but, as stated above, Laveran 

 holds this to be an artefact. The organism divides longitudin- 

 ally in the usual manner, and often two can be seen to approach 

 each other and lie more or less side by side, but whether this 

 indicates conjugation or not is not known. The organism does 

 not usually long survive removal from the body, but it has been 

 found to be motile for nineteen days when kept on rabbit-blood 

 agar at 22 C. As we have said, when Tr. ugandense is in- 

 oculated into monkeys they often contract an illness which 

 ultimately presents the features of typical sleeping sickness. 



